package main

import (
	"fmt"
	"math"
)

type Shape interface {
	Area() float64
}

type Circle struct {
	radius float64
}

func (C *Circle) Area() float64 {
	return math.Pi * C.radius * C.radius
}

func main() {

	c := Circle{}
	c.radius = 5
	fmt.Println(c.Area())

	C := Circle{radius: 65}
	fmt.Println(C.Area())

}
